U.S. patent number 11,049,794 [Application Number 14/194,701] was granted by the patent office on 2021-06-29 for circuit board with phase change material.
This patent grant is currently assigned to ADVANCED MICRO DEVICES, INC.. The grantee listed for this patent is ADVANCED MICRO DEVICES, INC.. Invention is credited to Manish Arora, Nuwan Jayasena.
United States Patent |
11,049,794 |
Arora , et al. |
June 29, 2021 |
Circuit board with phase change material
Abstract
Various circuit board embodiments are disclosed. In one aspect,
an apparatus is provided that includes a circuit board and a first
phase change material pocket positioned on or in the circuit board
and contacting a surface of the circuit board.
Inventors: |
Arora; Manish (Dublin, CA),
Jayasena; Nuwan (Sunnyvale, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
ADVANCED MICRO DEVICES, INC. |
Santa Clara |
CA |
US |
|
|
Assignee: |
ADVANCED MICRO DEVICES, INC.
(Santa Clara, CA)
|
Family
ID: |
1000005644111 |
Appl.
No.: |
14/194,701 |
Filed: |
March 1, 2014 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150249044 A1 |
Sep 3, 2015 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
23/4275 (20130101); H05K 1/0203 (20130101); H01L
2924/15313 (20130101); H01L 24/16 (20130101); H05K
3/3436 (20130101); H01L 2924/15311 (20130101); H01L
2924/15192 (20130101); H01L 2924/19042 (20130101); H01L
2224/16225 (20130101); H01L 2924/19041 (20130101); H05K
3/4697 (20130101); H01L 2224/131 (20130101); H01L
2924/19105 (20130101); H01L 24/13 (20130101); H01L
2924/19043 (20130101); H01L 2924/15312 (20130101); H01L
2224/131 (20130101); H01L 2924/014 (20130101) |
Current International
Class: |
H01L
23/373 (20060101); H01L 23/427 (20060101); H05K
1/02 (20060101); H01L 23/00 (20060101); H05K
3/46 (20060101); H05K 3/34 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
US. Appl. No. 14/016,063, filed Aug. 31, 2013, Arora et al. cited
by applicant .
U.S. Appl. No. 14/218,801, filed Mar. 18, 2014, Arora et al. cited
by applicant .
Wikipedia; Computer Cooling;
http://en.wikipedia.org/wiki/Computer_cooling; Dec. 13, 2012; pp.
1-16. cited by applicant .
Wikipedia; Phase-change Material;
http://en.wikipedia.org/wiki/Phase-change_material; Dec. 13, 2012;
pp. 1-16. cited by applicant .
Arun Raghavan et al.; Computational Sprinting; In the Proceedings
of the 18.sup.th Symposium on High Performance Computer
Architecture (HPCA 2012); 2012; pp. 1-12. cited by applicant .
USPTO Office Action notification date Mar. 2, 2015; U.S. Appl. No.
14/016,063. cited by applicant .
USPTO Office Action notification date Sep. 4, 2014; U.S. Appl. No.
14/016,063. cited by applicant .
Midel; Dielectric Insulating Fluid Overview; www.midel.com; Dec.
2010; pp. 1-2. cited by applicant .
Midel; Natural Ester Dielectric Insulating Fluid Overview;
www.midel.com; Mar. 2014; pp. 1-2. cited by applicant .
USPTO Office Action notification date Nov. 19, 2015; U.S. Appl. No.
14/218,801. cited by applicant.
|
Primary Examiner: Phan; Huy Q
Assistant Examiner: Clarke; Adam S
Claims
What is claimed is:
1. An apparatus, comprising: a circuit board having a first means
for holding a phase change material; and plural pins projecting
into the circuit board to make thermal contact with the first means
for holding the phase change material and projecting out of the
circuit board to make thermal contact with a component configured
to be mounted on the circuit board.
2. The apparatus of claim 1, wherein the first means for holding
the phase change material comprises an internal space of the
circuit board holding the phase change material.
3. The apparatus of claim 1, wherein the first means for holding
the phase change material comprises a shell coupled to an exterior
of the circuit board.
4. The apparatus of claim 3, wherein the circuit board comprises
the component mounted on the exterior, the shell comprising a frame
positioned around the component.
5. The apparatus of claim 1, wherein the circuit board comprises an
exterior and the component mounted on the exterior, the first means
for holding the phase change material being positioned beneath the
component.
6. The apparatus of claim 1, wherein the circuit board comprises a
second means for holding a phase change material.
7. The apparatus of claim 1, comprising a semiconductor chip
mounted on the circuit board and having a phase change material
pocket.
8. The apparatus of claim 1, comprising an electronic device
coupled to the circuit board.
9. A method of manufacturing, comprising: providing a circuit
board; forming an internal space in the circuit board; and after
forming the internal space positioning a phase change material in
the internal space to contact a surface of the circuit board.
10. The method of claim 9, positioning plural pins that project
into the circuit board to make thermal contact with the phase
change material and project out of the circuit board to make
thermal contact with a component configured to be mounted on the
circuit board.
11. The method of claim 9, comprising coupling a first phase change
material pocket to a first exterior side of the circuit board.
12. The method of claim 11, coupling a second phase change material
pocket to a second exterior side of the circuit board opposite to
the first exterior side, the second phase changer material pocket
comprising a frame configured to be positioned around a component
configured to be mounted on the circuit board.
13. The method of claim 11, wherein the first phase change material
pocket is positioned beneath the component.
14. The method of claim 9, comprising providing the circuit board
with a means for holding a phase change material.
15. The method of claim 9, comprising mounting a semiconductor chip
on the circuit board, the semiconductor chip having a phase change
material pocket.
16. A method of providing thermal management for a component
mounted on a circuit board, comprising: placing a first means for
holding a phase change material in thermal contact with the circuit
board; and using plural pins projecting into the circuit board to
make thermal contact with the first means for holding a phase
change material and projecting out of the circuit board to make
thermal contact with the component.
17. The method of claim 16, wherein the first means for holding the
phase change material is positioned in an internal space of the
circuit board.
18. The method of claim 16, wherein the first means for holding the
phase change material comprises a shell coupled to an exterior of
the circuit board.
19. The method of claim 16, comprising providing the component with
a second means for holding a phase change material.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to electronic devices, and more
particularly to structures and methods for providing thermal
management of electronic devices, including circuit boards.
2. Description of the Related Art
Circuit boards, such as printed circuit boards, are used in a vast
array of electronic devices. Examples of such devices are legion,
and include devices as diverse as walkie talkies and numerically
controlled lathes. A typical conventional circuit board includes a
substrate upon which several components are mounted. The components
can include integrated circuits, and passive devices such as
capacitors, resistors and inductors. In some applications, the
circuit board itself or one or more components mounted thereon may
dissipate sufficient amounts of heat that thermal management may be
necessary. This may be due to the potential for the undissipated
heat to adversely affect the performance or damage components of
the device and/or for the heat to cause the temperature of the
device in question to climb above a comfortable level for user
handling.
Heat sinks have been used for many years to dissipate heat
generated by circuit board components. Conventional heat sinks are
manufactured in a large variety of shapes and sizes. Many include
multiple heat fins projecting from a base member. Others include
heat pipes. Copper and aluminum are common conventional heat sink
materials due to their favorable conductive heat transfer
characteristics.
Conventional heat sinks have the disadvantage of consuming space.
In systems with large internal spaces, such as desktop computers
with large cases, big heat sinks may be easily accommodated. Thin
devices, such as tablet computers, represent a bigger technical
challenge, since internal space in such devices is limited. Some
designers have turned to flattened heat sinks for confined spaces.
However, conventional flattened heat sinks may give way to the
continuing drive to shave millimeters off the thicknesses of
computing devices.
The present invention is directed to overcoming or reducing the
effects of one or more of the foregoing disadvantages.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, an
apparatus is provided that includes a circuit board and a first
phase change material pocket positioned on or in the circuit board
and contacting a surface of the circuit board.
In accordance with another aspect of the present invention, a
method of manufacturing is provided that includes providing a
circuit board and positioning a first phase change material pocket
on or in the circuit board to contact a surface of the circuit
board.
In accordance with another aspect of the present invention, a
method of providing thermal management for a component mounted on a
circuit board is provided. The method includes positioning a first
phase change material pocket on or in the circuit board. Thermal
contact between the phase change material pocket and the component
is established.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing and other advantages of the invention will become
apparent upon reading the following detailed description and upon
reference to the drawings in which:
FIG. 1 is a pictorial view of an exemplary embodiment of a
semiconductor chip device 100 that includes a circuit board and
plural components;
FIG. 2 is a sectional view of FIG. 1 taken at section 2-2;
FIG. 3 is a portion of FIG. 2 shown at greater magnification;
FIG. 4 is a sectional view of FIG. 1 taken at section 4-4;
FIG. 5 is a sectional view of FIG. 1 taken at section 5-5;
FIG. 6 is a sectional view like FIG. 5 but of an alternate
exemplary embodiment of a circuit board;
FIG. 7 is a sectional view like FIG. 2 but of an alternate
exemplary circuit board;
FIG. 8 is a sectional view like FIG. 7 but of another alternate
exemplary circuit board;
FIG. 9 is a sectional view of FIG. 3 but depicting an initial
processing to establish a circuit board internal space;
FIG. 10 is a sectional view like FIG. 9 but depicting application
of a phase change material;
FIG. 11 is a sectional view like FIG. 10 but depicting fabrication
of one or more additional layers on the circuit board;
FIG. 12 is a sectional view like FIG. 11 but depicting application
of an alternate exemplary phase change material pocket to a circuit
board;
FIG. 13 is a sectional view like FIG. 12 but depicting another
alternate exemplary application of a phase change material pocket
to a circuit board;
FIG. 14 is a pictorial view depicting another alternate exemplary
phase change material pocket;
FIG. 15 is a sectional view of an exemplary semiconductor chip
incorporating phase change material pockets mounted on a circuit
board incorporating a phase change material pocket; and
FIG. 16 is a pictorial view of a circuit board 105 exploded from an
electronic device.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
Various circuit board arrangements are disclosed. The disclosed
embodiments incorporate one or more phase change material pockets
on or in a circuit board. The phase change material readily absorbs
and stores heat during phase change and thus facilitates heat
management for the circuit board and/or components mounted thereon.
Additional details will now be described.
In the drawings described below, reference numerals are generally
repeated where identical elements appear in more than one figure.
Turning now to the drawings, and in particular to FIG. 1, therein
is shown a pictorial view of an exemplary embodiment of a
semiconductor chip device 100 that includes a circuit board 105
upon which plural components may be mounted. A few of these
components are illustrated and labeled 110, 115, 120, 125, 130,
135, 140 and 145 respectively. The components 110, 115, 120, 125,
130, 135, 140 and 145 may be virtually any type of electronic or
electric component that may be mounted to a circuit board. Examples
include packaged semiconductor chips, optical devices such as
lasers, passive components such as inductors, capacitors and
resistors, etc., or other devices. The types of semiconductor chips
are legion and include processors, optical devices, communications
chips, system-on-chips or virtually any other type of electronic
functionality. The circuit board 105 may be a laminate construction
consisting of plural layers that are brought together either in a
sandwich fashion or as build up layers on a central core. The
circuit board 105 may include multitudes of internal and external
conductor traces. A few exemplary surface traces are depicted and
labeled collectively 150. Here, the circuit board 105 has a
generally rectangular form factor or footprint. However, the
skilled artisan will appreciate that the circuit board 105 may have
virtually any footprint.
Although not visible in FIG. 1, the circuit board 105 may be
provided with one or more PCM pockets that are designed to provide
thermal management for one or more of the components 110, 115, 120,
125, 130, 135, 140 and 145. Additional details of some of these PCM
pockets may be understood by referring now also to FIG. 2, which is
a sectional view of FIG. 1 taken at section 2-2. Note that because
of the location of section 2-2, the component 110 and the component
145 will appear in section. Here, the component 110 may consist of
a packaged semiconductor chip 155 that is mounted on a package
substrate 160. The semiconductor chip 155 may interface
electrically with the package substrate 160 in a variety of ways.
In this illustrative embodiment, a plurality of solder joints 165
such as solder bumps, microbumps or conductive pillars may be used
to interface the chip 155 with the package substrate 160. The
package substrate 160, may, in turn, electrically interface with
the circuit board 105 by way of the depicted ball grid array 170.
Optionally, a myriad of other types of interface schemes, such as,
pin grid arrays, land grid arrays, conductive pillars, lead frames,
etc. may be used to interface the substrate 160 with the circuit
board 105. To provide thermal management for the component 110, the
circuit board 105 may be provided with a PCM pocket 175 positioned
in the circuit board 105 beneath the location of the component 110.
As discussed elsewhere, there may be more than one PCM pocket 175
associated with the circuit board 105, and a PCM pocket may be
positioned on or in the circuit board 105.
A PCM pocket, such as the PCM pocket 175, includes a volume of a
PCM that will readily absorb and store heat while undergoing a
change of physical phase, say from solid to liquid or from one
solid phase to another. The heat can be released later during
periods of reduced power consumption by one or all of the
structures of the circuit board 105. The PCM pocket 175 and any
alternatives thereof may be so-called solid-to-liquid phase
materials or solid phase-to-solid phase materials. A large variety
of different types of PCMs may be used. In general, there are three
varieties of PCMs: (1) organic; (2) inorganic; and (3) eutectic.
These categories may be further subdivided as follows:
TABLE-US-00001 TABLE 1 PCM MATERIAL CLASSIFICATION ORGANIC
INORGANIC EUTECTIC Paraffin Salt Hydrate Organic-Organic
Non-Paraffin Metallic Inorganic-Inorganic Inorganic-Organic
A variety of characteristics are desirable for the material(s)
selected for the PCM pocket(s) 175 and any alternatives. A
non-exhaustive list of the types of desired PCM characteristics
includes a melting temperature T.sub.m less than but close to the
maximum anticipated chip operating temperature T.sub.max, a high
latent heat of fusion, a high specific heat, a high thermal
conductivity, small volume change and congruent melting (for
solid-to-liquid), high nucleation rate to avoid supercooling,
chemical stability, low or non-corrosive, low or no toxicity,
nonflammability, nonexplosive and low cost/high availability. Some
of these characteristics may be favored over others for a given
PCM. Table 2 below illustrates some exemplary materials for the PCM
pocket(s) 175 and any alternatives.
TABLE-US-00002 TABLE 2 Melting Point Latent Heat of Material
T.sub.m (.degree. C.) Fusion (kJ/kg) Notes Paraffin The numbers in
21 40.2 200 the first column 22 44.0 249 represent the 23 47.5 232
number of carbon 24 50.6 255 atoms for a given 25 49.4 238 form of
paraffin 26 56.3 256 27 58.8 236 28 61.6 253 29 63.4 240 30 65.4
251 31 68.0 242 32 69.5 170 33 73.9 268 34 75.9 269 Hydrocinnamic
acid 48.0 118 Cetyl alcohol 49.3 141 .alpha.-Nepthylamine 50.0 93
Camphene 50 238 O-Nitroaniline 50.0 93 9-Heptadecanone 51 213
Thymol 51.5 115 Methyl behenate 52 234 Diphenyl amine 52.9 107
p-Dichlorobenzene 53.1 121 Oxalate 54.3 178 Hypophosphoric acid 55
21 O-Xylene dichloride 55.0 121 .beta.-Chloroacetic acid 56.0 147
Chloroacetic acid 56 130 Nitro naphthalene 56.7 103 Trimyristin
33-57 201-213 Heptaudecanoic acid 60.6 189 .alpha.-Chloroacetic
acid 61.2 130 Bees wax 61.8 177 Glyolic acid 63.0 109 p-Bromophenol
63.5 86 Azobenzene 67.1 121 Acrylic acid 68.0 115 Dinto toluent (2,
4) 70.0 111 Na.sub.2HPO.sub.4.cndot.12H.sub.2O 40.0 279
CoSO.sub.4.cndot.7H.sub.2O 40.7 170 KF.cndot.2H.sub.2O 42 162
MgI.sub.2.cndot.8H.sub.2O 42 133 CaI.sub.2.cndot.6H.sub.2O 42 162
K.sub.2HPO.sub.4.cndot.7H.sub.2O 45.0 145
Zn(NO.sub.3).sub.2.cndot.4H.sub.2O 45 110
Mg(NO.sub.3).cndot.4H.sub.2O 47.0 142 Ca(NO.sub.3).cndot.4H.sub.2O
47.0 153 Fe(NO.sub.3).sub.3.cndot.9H.sub.2O 47 155
Na.sub.2SiO.sub.3.cndot.4H.sub.2O 48 168
K.sub.2HPO.sub.4.cndot.3H.sub.2O 48 99
Na.sub.2S.sub.2O.sub.3.cndot.5H.sub.2O 48.5 210
MgSO.sub.4.cndot.7H.sub.2O 48.5 202
Ca(NO.sub.3).sub.2.cndot.3H.sub.2O 51 104
Zn(NO.sub.3).sub.2.cndot.2H.sub.2O 55 68 FeCl.sub.3.cndot.2H.sub.2O
56 90 Ni(NO.sub.3).sub.2.cndot.6H.sub.2O 57.0 169
MnCl.sub.2.cndot.4H.sub.2O 58.0 151 MgCl.sub.2.cndot.4H.sub.2O 58.0
178 CH.sub.3COONa .cndot.3H.sub.2O 58.0 265
Fe(NO.sub.3).sub.2.cndot.6H.sub.2O 60.5 126
NaAl(SO.sub.4).sub.2.cndot.10H.sub.2O 61.0 181 NaOH .cndot.H.sub.2O
64.3 273 Na.sub.3PO.sub.4.cndot.12H.sub.2O 65.0 190
LiCH.sub.3COO.cndot.2H.sub.2O 70 150
Al(NO.sub.3).sub.2.cndot.9H.sub.2O 72 155
Ba(OH).sub.2.cndot.8H.sub.2O 78 265 Eladic acid 47 218 Lauric acid
49 178 Pentadecanoic acid 52.5 178 Tristearin 56 191 Myristic acid
58 199 Palmatic acid 55 163 Stearic acid 69.4 199 Gallium-gallium
29.8 --- The dashes antimony eutectic indicate the value is unknown
to the inventors at this time Gallium 30.0 80.3 Cerrolow eutectic
58 90.9 Bi--Cd--In eutectic 61 25 Cerrobend eutectic 70 32.6
Bi--Pb--In eutectic 70 29 Bi--In eutectic 72 25 Bi--Pb-tin eutectic
96 --- The dashes indicate the value is unknown to the inventors at
this time Bi--Pb eutectic 125 --- The dashes indicate the value is
unknown to the inventors at this time
To take advantage of the PCM pocket 175, it is necessary to provide
a thermally conductive pathway between the component 110 and the
PCM pocket(s) 175. This may be accomplished in a great variety of
ways. For example, and as illustrated in this exemplary embodiment,
the package substrate 160 may include vertically extending pins 177
and 178, which project down into the circuit board 105 and
establish thermal contact with the PCM pocket(s) 175. There may be
many more such pins that are not visible in FIG. 2 but used to
provide a thermal pathway between the component 110 and the PCM
pocket(s) 175. The pins 177 and 178 may be composed of well-known
thermally conductive materials, such as copper, silver, platinum,
gold, nickel, laminates or alloys of these, or other conductors. In
this illustrative embodiment, the PCM pocket(s) 175 may have a
generally sheet-like footprint. However, as described in more
detail below, the PCM pocket(s) 175 used in the circuit board 105
may have other types of shapes as desired.
The additional details of the component 145 will now be described
in conjunction with FIGS. 1 and 2. The component 145 may be a chip
scale package configuration as shown and interfaced electrically
with the circuit board 105 by way of the ball grid array balls 179
shown as with any of the other components, other types of
electrical interfaces may be used as well. Here, in lieu of the
pins 177 and 178, the thermal pathway between the component 145 and
a PCM pocket 180 positioned in the circuit board 105 may simply be
provided by way of the BGA balls 179. Although not visible due to
the scale of FIG. 2, the BGA 179 will establish metallurgical
connections with ball pads or other types of electrically
conductive surfaces of the circuit board 105 and these ball-to-pad
pathways may be used to provide the requisite thermal conductivity
between the component 145 and the PCM pocket 180. Still further
details of the component 145 and the PCM pocket 180 may be
understood by referring now also to FIG. 3, which is the portion of
FIG. 2 circumscribed by the dashed rectangle 181 in FIG. 2 shown at
greater magnification. Here, the aforementioned conductor pads,
three of which are labeled 185a, 185b and 185c, are shown in ohmic
contact with corresponding of the BGA balls 179. Various options
are available. For example, the pad 185a associated with its
corresponding ball may be configured as a dummy pad and used
principally as a thermal pathway between the component 145 and the
underlying PCM pocket 180. However, the pads 185b and 185c and
others may be electrically active. Optionally, conductive pathways
from the pads 185a, 185b and 185c into the circuit board may be
routed around the PCM pocket 200. Conductive heat transfer is
facilitated since the PCM pocket 180 is in contact with one or more
surfaces of the circuit board 105.
Some additional details of the circuit board 105 may be understood
by referring now to FIG. 4, which is a sectional view of FIG. 1
taken at section 4-4. Note that due to the location of section 4-4,
the components 120, 125 and 135 will be shown in section. Here, the
components 120, 125 and 135 may be chip scale package devices
connected to the circuit board 105 by way of respective BGAs 179.
The circuit board 105 may be a multi-layered structure consisting
of multiple layers 182a, 182b, 182c, 182d and 182e. The number and
types of layers 182a, 182b, 182c, 182d and 182e is subject to great
variation. For example, the layer 182b may be configured as a core
layer that provides strength while the layers 182a and 182c, 182d
and 182e may be interconnect layers. Many different types of
configurations are possible. In this illustrative embodiment, the
top most layer 182e is populated with the aforementioned conductor
pads, three of which are labeled 183a, 183b and 183c. Here, the
conductor pads 183b and 183c may electrically interface with other
conductor structures for example the conductor traces in the
interconnect layer 182c by way of conductive vias 184b and 184c.
The PCM pocket 180 is positioned in an internal space in the layer
182d. The internal space will be numbered and shown in greater
detail in subsequent figures. If the PCM pocket 180 is composed of
an electrically conducting material, then the layer 182d may be
patterned such that a given conductive via such as the via 183c may
be surrounded by a portion of the layer 182d as shown. Furthermore,
it may be easier from a manufacturing standpoint to provide such
conducting islands around a given conductive via in order to
facilitate a plating or other type of process to establish the
conducting via. The various layers 182a, 182b, 182c, 182d and 182e
may be composed of various well-known epoxies with or without
strengthening fillers such as glass fibers and others. In addition,
the layers 182a, 182b, 182c, 182d and 182e may be composed of so
called pre-preg layers that are stacked together and then heated to
construct a solid substrate. Various other materials such as
B-stage epoxies and others may be used as well. The components 120
and 125 may dissipate high enough levels of heat that it is
advisable to position PCM pockets 186 and 187 in the circuit board
105 beneath the positions of the components 120 and 125. The
aforementioned pins 177 and 178 may be used to establish a thermal
pathway between the components 120 and 125 and the PCM pockets 186
and 187, respectively. However, the component 135 may be small
enough or of sufficiently low power that it is not necessary to
position a PCM pocket in the circuit board beneath it as shown.
As just noted, PCM pockets may be placed in the circuit board 105
at locations where it is advantageous to provide additional thermal
management for various components. In this regard, attention is now
turned to FIG. 5, which is a sectional view of FIG. 1 taken at
section 5-5. Note that section 5-5 shows the circuit board 105 in
section but viewed from below. Here, the components 115, 130 and
135 are obscured and thus shown in phantom. In addition, the
components 115, 130 and 135 may not need PCM material and thus no
PCM material pockets are provided in the circuit board 105 at their
locations. The aforementioned PCM pockets 186 and 187 and an
additional PCM pocket 188 are visible. The PCM pocket 188 may be
positioned beneath the component 140 shown in FIG. 1. Here the PCM
pockets 175, 180, 186, 187 and 188 have generally rectangular
footprints, but other shapes are possible.
As noted above, the PCM pockets may have a variety of footprints.
In this regard, attention is now turned to FIG. 6, which is a
sectional view like FIG. 5 but of an alternate exemplary circuit
board 205 that may include the aforementioned PCM pockets 180, 186,
187 and 188. Again, the components 115, 130 and 135 may be mounted
without any PCM pockets and thus are shown in phantom. In the
embodiment depicted in FIG. 5, the PCM pocket 175 is sheet
structure. However, in the illustrative embodiment depicted in FIG.
6, the PCM pocket 275 is a frame-like structure so that an internal
portion 276 of the circuit board 205 inside the frame-like PCM
pocket 275 is available for electrical routing. Again, thermal
contact between a component and the PCM pocket 275 may be by any of
the alternatives disclosed herein.
Attention is now turned to FIG. 7, which is a sectional view like
FIG. 2 but of an alternate exemplary circuit board 305 that will be
used to illustrate various alternative usages and placements of PCM
pockets. Here, the component 110 may be mounted to the circuit
board 305 as generally described above with a few notable
exceptions. The aforementioned PCM pocket 175 may be positioned in
the circuit board 305 as generally described above in conjunction
with the circuit board 105. However, a PCM pocket 307 may be
mounted on an underside 309 of the circuit board 305 and in thermal
contact with the component 110 by way of the pin 178 which extends
from the component 110 down through the circuit board 305 and makes
thermal contact with the PCM pocket 307 as well as the PCM pocket
175. In addition, a frame-like PCM pocket 311 may be positioned on
an upper side 313 of the circuit board 305. The PCM pocket 311 may
be in thermal contact with the component 110 by way of the pins 177
and 178 as well as by thermally conductive contact with the package
substrate 160 as well. These externally-mounted PCM pockets 307 and
311 will include a container to hold a volume of PCM, but the scale
of FIG. 7 is such that these containers are not visible. Again, it
should be understood that the PCM pockets 175, 307 and 311 may be
configured and used in a variety of ways. The component 145 may be
positioned above the PCM pocket 180 as described above.
FIG. 8 is a sectional view like FIG. 7 but of yet another
alternative embodiment of a circuit board 405. In this illustrative
embodiment, the component 110 may be mounted to the circuit board
405 as generally described above in conjunction with the circuit
board 105. However, a PCM pocket 411 may be seated on an upper
surface 413 of the circuit board 405 and configured as a frame
structure that surrounds the component 110 and in particular
establishes thermal contact with the package substrate 160 thereof.
The PCM pocket 411 will consist of a shell 414 that encloses a
volume of PCM 416.
An exemplary method for fitting a circuit board with one or more
PCM pockets may be understood by referring now to FIGS. 9, 10 and
11 and initially to FIG. 9, which is a sectional view like FIG. 3
but at an earlier stage of processing. Up to this point, well known
techniques may be used to fabricate or otherwise join the
interconnect layers 182a, 182b, 182c and 182d. Furthermore, well
known interconnect fabrication techniques may be used to establish
the conductor traces 184a and 184b as well as the conductive vias
183b and 183c, etc. To hold the later applied or otherwise formed
PCM pocket, an internal space 517 is formed in the interconnect
layer 182d. The internal space 517 may be formed in a variety of
ways depending upon how the interconnect layer 182d is formed. For
example, if the interconnect layer 182d is a pre-preg layer then
the internal space 517 may be pre-patterned into the pre-preg layer
prior to application to the interconnect layer 182c. However, if
the interconnect layer 182d is a build up layer formed from an
epoxy rosin that is subsequently hardened, then the internal space
517 may be laser cut or chemically etched as desired. It may also
be possible to establish the internal space 517 by way of an
additive process such as lift off type process. Next and as shown
in FIG. 10, the PCM 180 may be applied into the internal space 517
by a suitable applicator 519. Optionally, the PCM 180 may be
applied as pre-forms that are placed in the internal space 517. At
this stage, the circuit board 105 is ready to have another
interconnect layer placed or otherwise formed on the interconnect
layer 182d.
As shown in FIG. 11, the interconnect layer 182e may be applied or
otherwise formed on the interconnect layer 182d and the conductor
pads, one of which is labeled 185b may be formed using well known
conductor pad fabrication techniques. At this stage, the PCM pocket
180 is enclosed and ready to provide thermal management. The
circuit board 105 may be subsequently processed to mount the
component 145 shown in FIG. 3 as well as any of the other
components shown in FIGS. 1 and 2.
As noted briefly above, a PCM pocket may be mounted in a variety of
locations relative to a circuit board. For example, an exemplary
circuit board 605 which may be substantially identical to the
circuit board 105 depicted in FIG. 11 may be fitted with a back
side PCM pocket 607 that consists of an enclosure 614 that holds a
volume of PCM 616. In addition, the circuit board 605 may include
the aforementioned front side PCM pocket 180 as described
above.
In another alternative embodiment depicted in FIG. 13, a circuit
board 705 may include the aforementioned front side PCM pocket 180.
However, in this illustrative embodiment, a PCM pocket 707 may be
embedded within one of the interconnect layers such as the
interconnect layer 182b of the circuit board 705. This may be
accomplished by, for example, forming an internal space 717 in the
interconnect layer 182b. Again, the material point here is to
illustrate that a PCM may be positioned in a variety of locations
in or on a circuit board.
In still another alternative embodiment, it may be possible to
place PCM in an external frame that is designed to fit around the
perimeter of an entire circuit board. This may be useful in
circumstances where it is not practical to reroute internal traces
and other conductors in a circuit board in order to accommodate
internally mounted PCM pockets. As shown in FIG. 14, a suitable
frame member 841 may be filled with a PCM 843. The frame 841 may
have a footprint with an internal opening 846 that is large enough
to accommodate the circuit board 105. A seating shelf 847 may be
positioned in the opening to allow the circuit board to be seated
thereon such that the circuit board 105 is on the frame member 841
and vice versa. The opening 846 is advantageously just slightly
larger than the circuit board 105 so that good thermal contact is
established between the frame 841 and the circuit board 105. The
frame 841 may be fabricated from a variety of materials such as
plastics, metals, etc.
As shown in FIG. 15, which is a sectional view of a small portion
of a circuit board 905, the usage of a PCM pocket 180 may be
extended to not only the circuit board 905 but also to a
semiconductor chip device that is mounted thereon. In this regard,
a chip device 923 may be mounted on the circuit board 905 and in
thermal contact with a PCM pocket 926 in the circuit board 905. The
semiconductor chip device 923 may include one or more semiconductor
chips 927 and 929 mounted on a substrate 931, which may be an
interposer or a circuit board. Each of the semiconductor chips 927
and 929 may be supplied with one or more PCM pockets 933.
Thru-silicon-vias 936 may be used for through chip routing of
power, ground and signals. The terms "thru-silicon" are not
intended to exclude chip materials other than silicon.
Any of the illustrative embodiments of a circuit board 105, 205,
305, 405, 505, 605, 705, 805 or 905 may be mounted in an electronic
device. For example, and as shown in FIG. 16, the circuit board 105
may be mounted into an electronic device 1003. The electronic
device 1003 may be a computer, a digital television, a handheld
mobile device, a personal computer, a server, a memory device, an
add-in board such as a graphics card, or any other computing device
employing semiconductors.
While the invention may be susceptible to various modifications and
alternative forms, specific embodiments have been shown by way of
example in the drawings and have been described in detail herein.
However, it should be understood that the invention is not intended
to be limited to the particular forms disclosed. Rather, the
invention is to cover all modifications, equivalents and
alternatives falling within the spirit and scope of the invention
as defined by the following appended claims.
* * * * *
References